Chemical processes may be said to be characterized by the handling of slurries or sludges. Usually the separation of a product from its medium in which it occurs or is formed involves a filtration operation, but it may also be useful in certain drying and flaking operations and also it may be useful as a traveling device to spread a uniform layer on a surface, for example cement or concrete from a traveling machine.
When used as a wash box on a traveling belt filter the liquor must be uniformly spread over the filter cake without stirring up or disturbing the cake.
A characteristic process of this kind is the formation of phosphoric acid by any traditional or wet method whether it be in the hemihydrate mode or the gypsum mode. The final aqueous medium will be a mixture of phosphoric acid with calcium sulphate, which is required to be filtered. This mobile solid-liquid mixture is passed to a filtration device and in a preferred type of operation to a moving belt filter. In this latter maneuver where the final filtration is on a moving belt and the washing occurs in stages along the belt, reasonably uniform distribution of slurry over the belt is most essential.
In a quite different kind of operation, movement of cellulose - aqueous pulp in paper making machinery is necessary, for example, from a head box into a paper-forming machine. This involves again a solid liquid slurry, whose handling is aided if it can be distributed uniformly across the section of the machine in which the movement is occuring.
In a related kind of operation, pouring of concrete involves an aqueous sludge, generally quite high in solid content, but, nevertheless, in pouring concrete for extended surfaces, a pour which gives a reasonable uniform distribution over a surface is most useful.
It is accordingly a basic object of this invention to provide a device suitable for use in chemical processing applications, wherein a solid-liquid sludge or slurry is being handled, so that the sludge can be fed into the device and spread relatively uniformly over a receiving surface as it makes its exit from the device.
Other objects and advantages of the invention will in part be obvious, and, in part, appear hereinafter.